The ultimate objective of the research is to provide respirators of substantially reduced weight aid size for use against toxic vapors in industrial work places. Phase I studies have established that breathing back through an absorbent filter significantly increases the filter life before breakthrough of toxic gases into the protected space. Phase II research will further develop this oscillatory flow concept with the goal of providing design and evaluation methods for practical respirators. Various absorber/toxic gas pairs will be identified that show promise of good performance. Their physical characteristics and absorptive capabilities will be obtained by literature searches and measurement. The Phase I mass transfer code will be expanded to include integration of mass and heat transfer and the effects of temperature on diffusion and absorption within polymer absorbers. Polymer data and the upgraded code will be utilized to determine the geometry and operating parameters for respirator absorbers optimized for size, weight and pressure loss ill breathing. An experimental apparatus will be constructed and used to measure respirator performance and to confirm the design procedure. Preliminary engineering studies will be made to assess practical issues of user comfort, wearability face mask leakage and methods of mass production.